The present invention relates to a disc brake which is advantageously used for imparting a braking force to a vehicle.
In general, a disc brake comprises: a mounting member mounted on a non-rotatable portion of a vehicle; a caliper displaceable in an axial direction of the disc relative to the mounting member and adapted to press friction pads against the disc; guide bores formed in one of the mounting member and the caliper and extending in the axial direction of the disc; sliding pins attached to the other of the mounting member and the caliper and inserted into the guide bores so as to support the caliper in a slidable manner; and protective boots for protecting slide surfaces of the guide bores and the sliding pins (as is disclosed in, for example, Unexamined Japanese Patent Application Public Disclosure Nos. 10-331879 and 11-108089).
A disc brake of the above-mentioned type in the related art is described below, with reference to FIGS. 18 to 20. In the drawings, reference numeral 1 denotes a mounting member integrally attached to a non-rotatable portion of a vehicle. The mounting member 1 includes a pair of arms 1A separated in a circumferential direction of a disc 16 (described later) and extending over an outer periphery of the disc 16 in an axial direction thereof. A pair of friction pads 3 (described later) are adapted to be guided in the axial direction of the disc 16 between the arms 1A.
Reference numeral 2 denotes a caliper slidably supported by the mounting member 1 through sliding pins 7 described later. The caliper 2 comprises a bridge portion 2A extending over the outer periphery of the disc 16 between the arms 1A of the mounting member 1, an inner leg portion 2B provided on an inner side of the bridge portion 2A and having a cylinder bore (not shown) defined by an inner circumferential surface thereof and an outer leg portion 2C provided on an outer side of the bridge portion 2A. Further, pin mounting portions 2D protrude from the inner leg portion 2B in leftward and rightward directions in FIG. 18, with the sliding pins 7 being attached thereto.
The friction pads 3 are positioned at opposite sides of the disc 16 between the arms 1A of the mounting member 1. The friction pads 3 are adapted to be slidably guided in the axial direction of the disc 16 between the arms 1A of the mounting member 1 and pressed against opposite surfaces of the disc 16 by the caliper 2.
Reference numeral 4 denotes a pair of guide bores which are formed in the arms 1A, respectively. Each guide bore 4 is a hole having a bottom and having a circular cross-section, and extends in the axial direction of the disc 16. Each sliding pin 7 is slidably inserted into the guide bore 4 and guided in the axial direction.
Reference numeral 5 denotes a cylindrical protrusion extending from each arm 1A of the mounting member 1 radially outward of the guide bore 4. As shown in FIG. 19, a first boot mounting groove 6 is formed in an outer circumferential surface of the cylindrical protrusion 5. The first boot mounting groove 6 includes side surfaces 6A and 6B and extends along an entire circumference of the cylindrical protrusion 5.
The reference numeral 7 denotes the pair of sliding pins 7. The sliding pins 7 are attached to pin mounting portions 2D of the caliper 2 and each includes a pin shaft portion 7A in a cylindrical form having a generally constant outer diameter. The pin shaft portion 7A has one end thereof slidably inserted into the guide bore 4 and the other end thereof protruding from the guide bore 4. The protruding end of the pin shaft portion 7A is connected to an annular protruding portion 7B protruding in a radially outward direction thereof and a caliper fixed portion 7C in a hexagonal form integrally connected to the annular protruding portion 7B on a side thereof opposite the pin shaft portion 7A.
An outer circumferential surface of the protruded end side of the pin shaft portion 7A includes a second boot mounting groove 8 positioned between the annular protruding portion 7B and the caliper fixed portion 7C and having side surfaces 8A and 8B and also includes a tapering guiding surface 9 extending between an outer circumferential surface of the pin shaft portion 7A and an outer circumferential surface of the annular protruding portion 7B so as to increase a diameter of the sliding pin 7 in a direction from the pin shaft portion 7A to the annular protruding portion 7B. As is described later, the guiding surface 9 is adapted to guide a pin-side mounting portion 15 of a protective boot 11 toward the second boot mounting groove 8. Further, the caliper fixed portion 7C of the sliding pin 7 is fixed to the pin mounting portion 2D of the caliper 2 by means of a pin bolt 10.
Each of the protective boot 11 is adapted to protect slide surfaces of the guide bore 4 and the sliding pin 7. As shown in FIG. 19, the protective boot 11 is formed as a bellowslike cylindrical body made of an elastic material, such as rubber, and disposed so as to enclose the sliding pin 7.
The protective boot 11 comprises a bellows portion 12 in the form of a cylinder enclosing the sliding pin 7 and adapted to extend and contract in the axial direction, a guide-bore-side mounting portion 13 connected to one end of the bellows portion 12 and mounted with an interference fit into the first boot mounting groove 6 of the mounting member 1, and the above-mentioned pin-side mounting portion 15 connected to the other end of the bellows portion 12 through a connecting portion 14 and mounted with an interference fit into the second boot mounting groove 8 of the sliding pin 7. The protective boot 11 provides a seal against entry of a foreign matter such as dust or rain water into an area between slide surfaces of the guide bore 4 and the sliding pin 7.
The disc 16 is adapted to rotate together with a wheel of the vehicle. The friction pads 3 apply a braking force to the disc 16 during a braking operation.
In the above-mentioned disc brake in the related art, a brake fluid is externally supplied to the inner leg portion 2B (cylinder bore) of the caliper 2, to thereby effect a sliding motion of a piston (not shown) in the cylinder bore and press the inner-side friction pad 3 against the disc 16.
In this instance, the caliper 2 receives a reaction force acting in a direction away from an inner side of the disc 16 and the sliding pin 7 integral to the caliper 2 slidably moves in the same direction through the guide bore 4 of the mounting member 1, to thereby enable the caliper 2 to press the outer-side friction pad 3 against the disc 16. Consequently, the disc 16 receives a braking force applied from opposite sides thereof by the friction pads 3.
Next, referring to FIG. 20, a description is made with regard to an operation for mounting of the protective boot 11. First, prior to insertion of the sliding pin 7 into the guide bore 4 of the mounting member 1, the guide-bore-side mounting portion 13 of the protective boot 11 is fitted into the first boot mounting groove 6 of the mounting member 1, to thereby attach the protective boot 11 to the mounting member 1 in a state such that it freely extends from the mounting member 1.
Subsequently, using an automatic mounting apparatus (not shown), the pin shaft portion 7A of the sliding pin 7 is inserted through the pin-side mounting portion 15 of the protective boot 11 into the boot and gradually inserted into the guide bore 4 of the mounting member 1 in a direction indicated by an arrow A.
Consequently, as shown in FIG. 20, the guiding surface 9 of the sliding pin 7 is brought into sliding contact with the pin-side mounting portion 15 of the protective boot 11. When the sliding pin 7 is further inserted into the guide bore 4, the bellows portion 12 of the protective boot 11 is subject to compressive deformation, and air sealably contained in an annular space S between the protective boot 11 and the sliding pin 7 is compressed. In this instance, the pin-side mounting portion 15 slidably moves along the guiding surface 9 toward the second boot mounting groove 8 in a direction indicated by an arrow B. The pin-side mounting portion 15 moves over the annular protruding portion 7B of the sliding pin 7 and is mounted with an interference fit into the second boot mounting groove 8.
In the above-mentioned related art, when the sliding pin 7 is inserted into the guide bore 4 for mounting of the protective boot 11, the pin-side mounting portion 15 of the protective boot 11 is moved over the annular protruding portion 7B of the sliding pin 7 and mounted with an interference fit into the second boot mounting groove 8, under the action of air pressure in the annular space S.
However, the above-mentioned related art is problematic in the following points. When the sliding pin 7 is inserted in the direction A in FIG. 20 into the guide bore 4, the pin-side mounting portion 15 of the protective boot 11, which is made of a material having a large frictional resistance, such as rubber, is dragged by the guiding surface 9 of the sliding pin 7 due to the frictional resistance. In this case, the pin-side mounting portion 15 is likely to bend in a direction indicated by an arrow Bxe2x80x2 and be wrapped or folded inside the bellows portion 12.
Therefore, in the related art, an operator must temporarily stop the operation of the automatic mounting apparatus and manually pull the pin-side mounting portion 15 out of the bellows portion 12 for appropriate re-attachment of the pin-side mounting portion 15 to the second boot mounting groove 8. Therefore, operations for mounting and replacement of the protective boot 11 become laborious.
Further, the pressure of air sealably contained in the annular space S acts through the protective boot 11 in a direction for pulling the sliding pin 7 out of the guide bore 4. Therefore, if the sliding pin 7 is not held after mounting of the protective boot 11, the sliding pin 7 is likely to protrude from the mounting member 1 in a floating state, under the action of air pressure in the annular space S, and disturbs an operation for mounting of the caliper 2 subsequent to the mounting of the protective boot 11.
The present invention has been made, in view of the above problems accompanying the related art. It is an object of the present invention to provide a disc brake wherein a pin-side mounting portion of a protective boot can be easily attached to a sliding pin and an operation for mounting of the protective boot can be smoothly conducted.
In order to achieve the above-mentioned object, the present invention provides a disc brake comprising: a mounting member mounted on a non-rotatable portion of a vehicle; a caliper displaceable in an axial direction of the disc relative to the mounting member and adapted to press a pair of friction pads against the disc; a guide bore formed in one member selected from the mounting member and the caliper and extending in the axial direction of the disc; a sliding pin attached to the other member of the mounting member and the caliper and inserted into the guide bore so as to support the caliper in a slidable manner; and a protective boot adapted to protect slide surfaces of the sliding pin and the guide bore. The protective boot comprises: a bellows portion in a cylindrical form enclosing the sliding pin and capable of extending or expanding and contracting in an axial direction of the sliding pin; a guide-bore-side mounting portion connected to one end of the bellows portion and attached to the mounting member or caliper at a position around an open end of the guide bore; a cylindrical portion formed between the guide-bore-side mounting portion and the bellows portion and axially extending around the sliding pin; a thick-walled portion connected to the other end of the bellows portion and having a greater wall thickness than the bellows portion so as to increase stiffness of the protective boot, the thick-walled portion having a radial size substantially equal to a radial size of the cylindrical portion; a thin-walled portion having one end thereof connected to the thick-walled portion on a side thereof opposite the bellows portion and having a smaller wall thickness than the thick-walled portion, the thin-walled portion being capable of bending axially and radially; and a pin-side mounting portion having one end thereof connected to the thin-walled portion on a side thereof opposite the thick-walled portion and attached with an interference fit to an outer circumferential surface of the sliding pin.
By this arrangement, when an end portion of the protective boot bends radially inward due to frictional resistance imparted to the pin-side mounting portion, the thick-walled portion having high stiffness abuts against the pin-side mounting portion through the thin-walled portion, to thereby prevent the pin-side mounting portion from bending to an undesirable extent and being wrapped inside the bellows portion. Further, the cylindrical portion and the thick-walled portion have substantially the same radial size. Therefore, the protective boot as a whole can be obtained in a generally cylindrical form extending along a predetermined cylindrical surface. The bellows portion can be smoothly extended and contracted along the cylindrical surface.
Consequently, it is possible to suppress radial buckling of the bellows portion when it is subject to compressive deformation, and a restoring force of the bellows portion can be stably applied to the pin-side mounting portion through the thick-walled portion.
In one embodiment of the present invention, an outer circumferential surface of the mounting member or caliper at a position around the guide bore may include a first boot mounting groove into which the guide-bore-side mounting portion of the protective boot is fitted and the outer circumferential surface of the sliding pin includes a second boot mounting groove into which the pin-side mounting portion of the protective boot is fitted. A length (L1) between the guide-bore-side mounting portion and the pin-side mounting portion as measured when the bellows portion of the protective boot is axially compressed to a large extent may be greater than a length (L2) between the first boot mounting groove and the second boot mounting groove as measured when the sliding pin is inserted to a maximum depth into the guide bore.
By this arrangement, when the sliding pin is inserted to a maximum depth into the guide bore, the length (L1) between the mounting portions when the protective boot is compressed to a large extent becomes greater than the length (L2) between the first and second boot mounting grooves. Therefore, the pin-side mounting portion can be reliably fitted into the second boot mounting groove.
In another embodiment of the present invention, the outer circumferential surface of the sliding pin may include a boot guiding portion for guiding the pin-side mounting portion of the protective boot in a direction from the guide bore to the second boot mounting groove.
By this arrangement, when the sliding pin is inserted into the guide bore, the pin-side mounting portion of the protective boot can be guided into the second boot mounting groove while being slidably moved along the boot guiding portion.
In a further embodiment of the present invention, the pin-side mounting portion may include a communication passage. The communication passage is adapted to bring a space formed between the protective boot and the sliding pin into communication with the outside, during mounting of the protective boot on the outer circumferential surface of the sliding pin.
By this arrangement, when the pin-side mounting portion of the protective boot is brought into sliding contact with the outer circumferential surface of the sliding pin during mounting of the protective boot, the pin-side mounting portion is inclined radially inward through the thin-walled portion due to the effect of frictional resistance relative to the sliding pin, and the communication passage of the pin-side mounting portion is positioned such that it is open to an annular space formed between the sliding pin and the protective boot. Consequently, the air which is compressed in the annular space during insertion of the sliding pin can be discharged through the communication passage to the outside.
The present invention also provides a disc brake comprising: a mounting member mounted on a non-rotatable portion of a vehicle; a caliper displaceable in an axial direction of the disc relative to the mounting member and adapted to press a pair of friction pads against the disc; a guide bore formed in one member selected from the mounting member and the caliper and extending in the axial direction of the disc; a sliding pin attached to the other member of the mounting member and the caliper and inserted into the guide bore so as to support the caliper in a slidable manner; and a protective boot adapted to protect slide surfaces of the sliding pin and the guide bore. The protective boot comprises: a bellows portion in a cylindrical form enclosing the sliding pin and capable of extending or expanding and contracting in an axial direction of the sliding pin; a guide-bore-side mounting portion connected to one end of the bellows portion and attached to the mounting member or caliper at a position around an open end of the guide bore; a thick-walled portion connected to the other end of the bellows portion and having a greater wall thickness than the bellows portion so as to increase stiffness of the protective boot; a thin-walled portion having one end thereof connected to the thick-walled portion on a side thereof opposite the bellows portion and having a smaller wall thickness than the thick-walled portion, the thin-walled portion being capable of bending axially and radially; and a pin-side mounting portion having one end thereof connected to the thin-walled portion on a side thereof opposite the thick-walled portion and attached with an interference fit to an outer circumferential surface of the sliding pin. An outer circumferential surface of the mounting member or caliper at a position around the guide bore includes a first boot mounting groove into which the guide-bore-side mounting portion of the protective boot is fitted and the outer circumferential surface of the sliding pin includes a second boot mounting groove into which the pin-side mounting portion of the protective boot is fitted. A length (L1) between the guide-bore-side mounting portion and the pin-side mounting portion as measured when the bellows portion of the protective boot is axially compressed to a large extent is greater than a length (L2) between the first boot mounting groove and the second boot mounting groove as measured when the sliding pin is inserted to a maximum depth into the guide bore.
By this arrangement, when an end portion of the protective boot bends radially inward due to frictional resistance imparted to the pin-side mounting portion, the thick-walled portion having high stiffness abuts against the pin-side mounting portion through the thin-walled portion, to thereby prevent the pin-side mounting portion from bending to an undesirable extent and being wrapped inside the bellows portion. Further, when the sliding pin is inserted to a maximum depth into the guide bore, the length (L1) between the mounting portions when the protective boot is compressed to a large extent becomes greater than the length (L2) between the first and second boot mounting grooves. Therefore, the pin-side mounting portion can be reliably fitted into the second boot mounting groove.
In one embodiment of the present invention, the outer circumferential surface of the sliding pin may include a boot guiding portion for guiding the pin-side mounting portion of the protective boot in a direction from the guide bore to the second boot mounting groove.
By this arrangement, when the sliding pin is inserted into the guide bore, the pin-side mounting portion of the protective boot can be guided into the second boot mounting groove while being slidably moved along the boot guiding portion.
In another embodiment of the present invention, the pin-side mounting portion may include a communication passage. The communication passage is adapted to bring a space formed between the protective boot and the sliding pin into communication with the outside, during mounting of the protective boot on the outer circumferential surface of the sliding pin.
By this arrangement, when the pin-side mounting portion of the protective boot is brought into sliding contact with the outer circumferential surface of the sliding pin during mounting of the protective boot, the pin-side mounting portion is inclined radially inward through the thin-walled portion due to the effect of frictional resistance relative to the sliding pin, and the communication passage of the pin-side mounting portion is positioned such that it is open to an annular space formed between the sliding pin and the protective boot. Consequently, the air which is compressed in the annular space during insertion of the sliding pin can be discharged through the communication passage to the outside.
The present invention further provides a disc brake comprising: a mounting member mounted on a non-rotatable portion of a vehicle; a caliper displaceable in an axial direction of the disc relative to the mounting member and adapted to press a pair of friction pads against the disc; a guide bore formed in one member selected from the mounting member and the caliper and extending in the axial direction of the disc; a sliding pin attached to the other member of the mounting member and the caliper and inserted into the guide bore so as to support the caliper in a slidable manner; and a protective boot adapted to protect slide surfaces of the sliding pin and the guide bore. The protective boot comprises: a bellows portion in a cylindrical form enclosing the sliding pin and capable of extending or expanding and contracting in an axial direction of the sliding pin; a guide-bore-side mounting portion connected to one end of the bellows portion and attached to the mounting member or caliper at a position around an open end of the guide bore; and a pin-side mounting portion connected to the other end of the bellows portion through a cylindrical connecting portion and attached with an interference fit to an outer circumferential surface of the sliding pin. The cylindrical connecting portion between the bellows portion and the pin-side mounting portion includes a reinforcing rib, which is formed along a part of an entire circumferential length of the cylindrical connecting portion, so as to suppress bending of the pin-side mounting portion toward a radially inner side of the connecting portion during mounting of the protective boot on the outer circumferential surface of the sliding pin.
By this arrangement, for mounting of the protective boot, the pin-side mounting portion is slidably moved along the outer circumferential surface of the sliding pin and attached with an interference fit to a mounting portion, such as a groove formed in the outer circumferential surface of the sliding pin. In this instance, the reinforcing rib prevents the pin-side mounting portion from bending toward a radially inner side of the connecting portion due to the effect of frictional resistance relative to the sliding pin and being wrapped inside the connecting portion.
In one embodiment of the present invention, the disc brake further may comprise a plurality of reinforcing ribs arranged in a spaced relationship in a circumferential direction of the protective boot.
By this arrangement, stiffness of the connecting portion can be increased at a plurality of positions in the circumferential direction.
In another embodiment of the present invention, the plurality of reinforcing ribs are arranged in a substantially equally spaced relationship in the circumferential direction of the protective boot.
By this arrangement, stiffness of the connecting portion can be increased uniformly in the circumferential direction.
In a further embodiment of the present invention, the pin-side mounting portion of the protective boot may include a communication passage for enabling air contained in a space formed between the protective boot and the sliding pin to be discharged to the outside during mounting of the protective boot on the outer circumferential surface of the sliding pin.
In this arrangement, during mounting of the protective boot, the connecting portion is subject to elastic deformation due to the frictional resistance generated between the pin-side mounting portion and the sliding pin, so that the pin-side mounting portion can be radially inclined through the connecting portion. Consequently, the communication passage can be positioned such that it is open to the annular space formed between the sliding pin and the protective boot. When the protective boot is compressed during mounting thereof, the air contained in the annular space can be discharged through the communication passage to the outside.
In a further embodiment of the present invention, the communication passage may be formed at a position different from position(s) of the reinforcing rib(s) with respect to the circumferential direction of the protective boot.
In this arrangement, a portion of the connecting portion of the protective boot, in which no reinforcing rib is formed, has flexibility, so that the communication passage can be disposed at a circumferential position corresponding to the flexible portion. Consequently, during mounting of the protective boot, the pin-side mounting portion can be smoothly inclined to a radially inner side thereof at the position in which the communication passage is formed, and the communication passage can be stably positioned such that it is open to the annular space inside the protective boot.
In the present invention, a space between the reinforcing ribs which circumferentially overlaps the communication passage may have a greater circumferential length than a space between the reinforcing ribs which does not overlap the communication passage.
By this arrangement, high flexibility can be imparted to a portion between the reinforcing ribs, which is located at a position corresponding to the communication passage, thereby further improving the performance of the communication passage to effect an escape of air.